Virtual Network Computing

VNC

Index
1. What is VNC
2. How VNC can be used
3. Getting Started with VNC
4. Running a Unix server
5. Running a Windows server
6. Running a Unix viewer
7. Running a Windows viewer
8. Using a web browser as a viewer

What is VNC

VNC stands for Virtual Network Computing. It is remote control software which allows you to view and interact with one computer using a simple program on another computer anywhere on the Internet. The two computers don't even have to be the same type. VNC is freely and publicly available and is in widespread active use by millions throughout industry, academia and privately.

The important factors which distinguish VNC from other remote display systems are as follows:

No state is stored at the viewer. This means you can leave your desk, go to another machine, whether next door or several hundred miles away, reconnect to your desktop from there and finish the sentence you were typing. Even the cursor will be in the same place.
It is truly platform-independent. A desktop running on a Linux machine may be displayed on a PC. Or a Solaris machine. Or any number of other architectures. There is a Java viewer so that any desktop can be viewed with any Java-capable browser. There is a Windows server, allowing you to view the desktop of a remote Windows machine on any of these platforms using exactly the same viewer.
It is small and simple.
It is sharable. One desktop can be displayed and used by several viewers at once

How VNC can be used?

VNC allows a person at a remote computer to assume control of another computer across a network, as if they were sitting in front of the other computer.

For example, VNC can be used to provide a flexible hot-desking and road-warrior environment by allowing employees to access their office desktop and server machines from any machine in the company's offices or from other remote sites, regardless of the type of computers involved at either end. An equally popular business application of VNC is in remote system administration, where VNC is used to allow administrators to take control of employee machines to diagnose and fix problems, or to access and administer server machines without making a trip to the console.

Getting Started with VNC

VNC consists of two types of component.

A server:
- runs on the computer you want to remotely access
- generates a display
A viewer:
- runs on the computere you are sitting in front of
- actually draws the display on your screen.

To get started with VNC you need to run a server, and then connect to it with a viewer. VNC software requires a TCP/IP connection between the server and the viewer. You'll need to know the name or IP address of the server when you connect a viewer to it.

Running a Unix server

To X applications, a VNC server appears just like the standard X display you sit in front of, but without a physical screen attached. The applications don't know this, they just carry on running whether or not a viewer is connected. You can start a new VNC server on a Unix machine by typing:

unix % vncserver

If you haven't run a VNC server before you will be prompted for a password, which you will need to use when connecting to this server. All your servers on the same Unix machine will use the same password, and you can change it at a later date using

unix % vncpasswd

With a normal X system, the main X display of a workstation called 'snoopy' is usually snoopy:0. You can also run as many VNC servers on a Unix machine as you like, and they will appear as snoopy:1, snoopy:2 etc, as if they were just additional displays. Normally vncserver will choose the first available display number and tell you what it is, but you can specify a display number if you always wish to use the same one:

unix % vncserver :2

You can cause applications to use a VNC server rather than the normal X display them by setting the DISPLAY environment variable to the VNC server you want, or by starting the application with the -display option. For example:

unix % xterm -display snoopy:2 &

You can kill a Unix VNC server using, for example:

unix % vncserver -kill :2

Nothing will appear immediately as a result of starting a Unix VNC server. To see anything you need to connect a viewer to the server.

Running a Windows server

If this is the first time you've used a VNC server on this machine you'll be prompted to set a password, which you'll need when you connect to the machine from a remote location. A small icon will appear in the system tray, and by right-clicking on this you can control most aspects of the server.

You can now go to another machine and connect a viewer to the server.

Running a UNIX viewer

If you have started a server as display 2 on machine snoopy, you can start a viewer for it by typing:

unix % vncviewer snoopy:2

Enter it and click OK, and you will be prompted for your password, after which you should see the remote display.

Running a Windows viewer

In this case, you will be prompted for the host name (VNC server name) and display number:

Enter it and click OK, and you will be prompted for your password, after which you should see the remote display. If you are connecting to a Windows or Mac server, the display number will be 0 unless you have explicitly changed it, and can be omitted.

You can run the viewer on Unix and Windows by typing at the command line:

vncviewer snoopy:2

You need to specify the name of the VNC server and the number of the desktop. If, for example, you have started a server as display 2 on a machine called 'snoopy'. Remember that if you are connecting to a Windows or Mac server, the display number will be 0 unless you have explicitly changed it, and can be omitted.

Using a web browser as a viewer

The VNC servers also contain a small web server. If you connect to this with a web browser, you can download the Java version of the viewer, and use this to view the server. You can then see your desktop from any Java-capable browser, unless you are using a proxy to connect to the web. The server listens for HTTP connections on port 5800+display number. So to view display 2 on machine 'snoopy', you would point your web browser at:

http://snoopy:5802/

The applet will prompt you for your password, and should then display the desktop.

This document was translated from L^AT_EX by H^EV^EA .